1. Field of the Invention
This invention relates to a multi-system air conditioning machine capable of air-conditioning a plurality of rooms.
2. Description of the Related Art
In multi-system air-conditioning machines, a plurality of indoor units are connected to a single outdoor unit.
In some of such air-conditioning machines, the outdoor unit contains a compressor, a water heat exchanger, and a receiver, and the indoor units each contain air heat exchangers.
The compressor, water heat exchanger, receiver, and a parallel circuit of air heat exchangers are connected to one another by means of piping so as to constitute a refrigeration cycle. With this configuration, use of the water heat exchanger increases the air-conditioning capability.
The water heat exchanger provides a heat exchange between the inflow refrigerant and the water supplied from an external water supply unit. The refrigerant gas discharged from the compressor is converted into a liquefied refrigerant at the water heat exchanger.
The receiver stores an excess of liquefied refrigerant generated due to variations in the air-conditioning load.
In conventional air-conditioning machines, however, it is difficult to store all of the surplus liquefied refrigerant in the receiver. For example, part of the liquefied refrigerant can always remain in the water heat exchanger. If this happens, the heat exchanging area of the water heat exchanger decreases, reducing the air-conditioning capability.
One multi-system air-conditioning machine is disclosed in Published Unexamined Japanese Patent Application No. 64-6657.
The reference numerals used in the discussion below refer to FIGS. 1 and 3 of published unexamined Japanese Patent Application No. 64-b 6657.
In the disclosed machine in which the outdoor unit is provided with a plurality of air heat exchangers 3 and 4 and indoor units are provided with air heat exchangers 11a and 11b, the inflow of refrigerant into the air heat exchangers 3 and 4 is controlled according to the number of indoor units operated.
Here, the outdoor unit of the air-conditioning machine is not provided with a water heat exchanger.
Another multi-system air-conditioning machine is disclosed in Published Examined Japanese Utility Model Application No. 54-685.
The reference numerals used in the discussion below refer to FIG. 1 of published unexamined Japanese Patent Application No. 54-685.
In this machine, the outdoor unit A is provided with a water heat exchanger 3. However, the application has no explanation in it for the possibility that the liquefied refrigerant might remain in the water heat exchanger 3 and a the way of removing the remaining refrigerant.